legalContractRef changed String to SecureHash (of contract contents)

src/contracts/Cash.kt

@@ -29,7 +29,16 @@ class InsufficientBalanceException(val amountMissing: Amount) : Exception()
  * vaults can ignore the issuer/depositRefs and just examine the amount fields.
  */
 object Cash : Contract {
-    override val legalContractReference: String = "https://www.big-book-of-banking-law.gov/cash-claims.html"
+    /**
+     * TODO:
+     * 1) hash should be of the contents, not the URI
+     * 2) allow the content to be specified at time of instance creation?
+     *  Motivation: it's the difference between a state object referencing a programRef, which references a
+     *  legalContractReference and a state object which directly references both.  The latter allows the legal wording
+     *  to evolve without requiring code changes. But creates a risk that users create objects governed by a program
+     *  that is inconsistent with the legal contract
+     */
+    override val legalContractReference: SecureHash = SecureHash.sha256("https://www.big-book-of-banking-law.gov/cash-claims.html");
 
     /** A state representing a cash claim against some institution */
     data class State(

src/contracts/CommercialPaper.kt

@@ -23,7 +23,8 @@ val CP_PROGRAM_ID = SecureHash.sha256("replace-me-later-with-bytecode-hash")
 
 // TODO: Generalise the notion of an owned instrument into a superclass/supercontract. Consider composition vs inheritance.
 object CommercialPaper : Contract {
-    override val legalContractReference: String = "https://en.wikipedia.org/wiki/Commercial_paper"
+    // TODO: should reference the content of the legal agreement, not its URI
+    override val legalContractReference: SecureHash = SecureHash.sha256("https://en.wikipedia.org/wiki/Commercial_paper")
 
     data class State(
         val issuance: InstitutionReference,

src/contracts/DummyContract.kt

@@ -18,5 +18,6 @@ object DummyContract : Contract {
         // Always accepts.
     }
 
-    override val legalContractReference: String = "/dev/null"
+    // The "empty contract"
+    override val legalContractReference: SecureHash = SecureHash.sha256("")
 }

src/contracts/JavaCommercialPaper.java

@@ -118,7 +118,8 @@ public class JavaCommercialPaper implements Contract {
 
     @NotNull
     @Override
-    public String getLegalContractReference() {
-        return "https://en.wikipedia.org/wiki/Commercial_paper";
+    public SecureHash getLegalContractReference() {
+        // TODO: Should return hash of the contract's contents, not its URI
+        return SecureHash.Companion.sha256("https://en.wikipedia.org/wiki/Commercial_paper");
     }
 }

src/core/Structures.kt

@@ -69,7 +69,9 @@ interface Contract {
      */
     fun verify(tx: TransactionForVerification)
 
-    // TODO: This should probably be a hash of a document, rather than a URL to it.
-    /** Unparsed reference to the natural language contract that this code is supposed to express (usually a URL). */
-    val legalContractReference: String
+    /**
+     * Unparsed reference to the natural language contract that this code is supposed to express (usually a hash of
+     * the contract's contents).
+     */
+    val legalContractReference: SecureHash
 }